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T O P I C R E V I E W

ASCAN1984

Would it have been possible to depressurise the Mercury spacecraft and perform an EVA?

garymilgrom

No. This spacecraft used a hatch that was bolted in place. With no one to bolt the hatch closed after the EVA the spacecraft could not return safely to Earth.

moorouge

Going off at a tangent - an EVA by a Mercury astronaut formed the basis of Martin Caidin's origin book 'Marooned'.

Wally Schirra, having read the book, is alleged to have said that there was one technical error in it but never divulged what it was. I wonder if it concerned this aspect of the rescue.

Headshot

I was going to bring up the Mercury EVA described in Marooned myself. To those that never read this wonderful 1964 book, a fictitous Mercury astronaut is marooned in orbit (retrorockets did not fire) and the U.S. send a Gemini spacecraft (with one seat empty) to rescue him while the Russions send a modified Vostok to do the same.

I have often wondered about that technical flaw Schirra discovered. Perhaps it is that a Mercury astronaut would not be able to exit the capsule in a fully pressurized suit.

Anyone out there have any ideas?

Jay Chladek

There are two versions of the book Marooned. The original 1964 book had the Mercury craft (I can't recall what the rescue craft was, if it was a Gemini or Dyna-soar). Then there is the 1968-70 version what was re-written by Caidin to fit the movie premise of an Apollo craft stuck in orbit. The only copy I have is the later one.

Concerning a Marooned rescue, with the later explosive hatch design on the Mercury craft, I imagine that could have been jettisoned, but the resulting delta-Vee from the jettison would have pushed the craft away a bit (I've never been able to get a 1964 copy of the book to read, so I am just speculating here). Who knows what hitting that plunger would have done to a suited hand though as the kick-back force hopefully wouldn't tear the coverings.

Schirra being the astronaut most closely associated with the suit testing probably would have referred to a technical error in that front. From what I can recall about Mercury suits, their time of pressurization after a full loss of cabin pressure was relatively low as it was emergency use only. Plus, their outer coverings were never intended to handle direct exposure to space, otherwise as soon as an astronaut got out if it were in sunlight, he would have started to get slow roasted like Gene Cernan's posterior when the thermal coverings tore on his Gemini suit back there on Gemini 9 during his EVA (but nobody had yet performed an eva in 1964).

As for anything else I can think of, Mercury suits had two attachments for lines. There was an umbilical pressurization line as I recall, plus a second line that fed oxygen to the helmet. Perhaps the error might have been that in comparison to what Caidin wrote in his text.

onesmallstep

Apart from the obvious reasons stated above (bolt-secured hatch, astronaut unable to exit craft fully pressurized) one more impediment comes to mind: no tether/oxygen umbilical long enough to reach another spacecraft, let alone 'spacewalk'. So the Gemini or Vostok rescuer would have to come to the Mercury capsule, and then connect an auxiliary oxygen pack or umbilical from the rescue ship. Only way I see a viable rescue in an extreme case.

moorouge

Just a couple of small points. The hatch on Mercury could be released from the outside by means of a lanyard and one assumes that any resulting Delta Vees could be compensated for by the Mercury capsule - it was only the retros that failed.

One question that hasn't been addressed is, was the Mercury suit totally compatible with the Gemini environmental systems? If not, wouldn't there be problems keeping the rescued astronaut alive even assuming a successful transfer? How long would an emergency re-entry take?

On edit - it's a long time since I read the book, but I assume that it is set in the period before Gemini became fully operational. Therefore, might the flaw be in the configuration of the early Gemini capsules?

robsouth

Could the top hatch not be used to exit the Mercury spacecraft?

Headshot

Probably not. The passage through the neck of the Mercury capsule is exceedingly narrow. I believe an astronaut in a pressurized space suit would find it impossible to make it through.

I reread part of the '64 version of Marooned last night. As info:

When Pruett (the stranded astronaut) blows Mercury's hatch, no mention is made of spacecraft attitude or translation motions caused by the hatch's departure.

Pruett has a small oxygen bottle that he straps to his leg. It has a 15 minute supply. A similar configuration is shown on the cover of the March 1964 issue of National Geographic magazine depicting a Gemini EVA.

Pruett has no difficulty exiting the Mercury capsule in his pressurized suit!

The emergency EVA takes place at night (illumination is supplied by the nearby Soviet Vostok, which is equipped with a floodlight), so there are no solar heating issues with the Mercury spacesuit.

Caidin (the author) emphasizes that both astronauts realize they must make slow, deliberate motions during their EVA or their movements will become uncontrollable.

There is no problem connecting Pruett's Mercury spacesuit to Gemini's ECS. This is fortunate at he only had one minute of oxygen left ... cue the drama.

It seems to be just as good a read as I remember. I will probably reread the whole book soon. It is certainly better than the Apollo/Skylab (or Ironman as they called it) version that Caidin put out later. I just wish Hollywood had done the movie based on the earlier, Mercury version.

Jay Chladek

Thanks for the summary. I need to find a copy of the 1964 version as I felt the later re-write wasn't entirely one of Caidin's best (probably because elements of the first story focusing on one guy stuck in orbit had to be transferred to three people total). The movie I still feel was relatively well done for what it was though.

Given how agonizingly slow Hollywood can be, it is amazing Marooned was optioned and made when it was. While the first story would potentially have been exciting, I've found that fiction based on "past" events told relatively soon after doesn't tend to draw in movie audiences as much as one with a premise where "this could still happen". Plus, Apollo was all the rage at that point and AAP (the space lab shown was pre-Skylab as it was a wet-lab based concept) was on the drawingboard for taking place very soon.

We can certainly credit the Marooned movie with help getting the ball rolling on ASTP as when the then president of the National Academy of Sciences told his Soviet counterparts about how the Soviet cosmonaut was protrayed in the film (while also stressing that the Soviets had turned down every previous opportunity to take part in joint space projects during the 1960s), they were positively shocked.

Getting back to the original question, doing the EVA at night at least helps in one regard, although the extreme cold of life in space shadow might cause other problems as well. Although, 15 minutes I suppose "might" be enough time. Not taking into account the delta vee and attitude situation if the hatch got blown is a bit of an oversight though as given how relatively light a Mercury is and how powerful those bolts were, I certainly wouldn't want to be in the general path of the spacecraft hatch if it popped off AT ALL. For an astronaut performing an EVA, trying to pull Mercury's external lanyard would also be just asking for trouble as well (the result being an astronaut AND a craft ending up turning as Pete Conrad might call it "a** over tea kettle").

Now the ironic bit is if anyone remembers the old classic GI Joe Mercury capsule from the 1960s with the astronaut figure, it was a guy in a Mercury suit set up with a chest pack for EVAs. I have to wonder if the book "Marooned" might have influenced Hasbro's decision to make that set.

moorouge

quote:Originally posted by Headshot: When Pruett (the stranded astronaut) blows Mercury's hatch, no mention is made of spacecraft attitude or translation motions caused by the hatch's departure.

This could well be the technical error Schirra to which alluded.

robsouth

The windows of two Mercury spacecraft were cracked when they blew the hatch following recovery so it packed a substantial force. Following the hatch incident on Mercury 4 a mechanical hatch was considered but this idea was dropped due to weight restrictions.

moorouge

quote:Originally posted by robsouth:The windows of two Mercury spacecraft were cracked when they blew the hatch following recovery so it packed a substantial force.

Curious as to know where this came from. The only window damage recorded in the final Mercury programme report was a small star shaped impact crater on the window of 'Faith 7'. This was thought to have been caused by a micro-meteorite strike.

robsouth

As far as I know both the Mercury Atlas 5 and 9 spacecraft suffered window damage following recovery.

carmelo

Marooned novel is set in 1964.

Was the Gemini G2C (silver) suit, available in 1964, compatible with the Mercury capsule?